Nerve growth factor (NGF) is a protein which has prominent effects on developing sensory and sympathetic neurons of the peripheral nervous systems. NGF acts via specific cells surface receptors on responsive neurons to support neuronal survival, promote neurite outgrowth, and enhance neurochemcial differentiation. NGF actions are accompanied by alterations in neuronal membranes (Connolly et al., J. Cell. Biol. 90:176-180 [1981]; Skaper and Varon, Brain Res. 197:379-389 [1980]), in the state of phosphorylation of neuronal proteins (Yu, et al., J. Biol. Chem. 255:10481-10492 [1980]; Haleqoua and Patrick, Cell 22:571-581 [1980]), and in the abundance of certain mRNAs and proteins likely to play a role in neuronal differentiation of function (see, for example, Tiercy and Shooter, J. Cell. Biol. 103:2367-2378 [1986]).
Forebrain cholinergic neurons also respond to NGF and may require NGF for trophic support. (Hefti, J. Neurosci., 6:2155 [1986]). Indeed, the distribution and ontogenesis of NGF and its receptor in the central nervous system (GNS) suggest that NGF acts as a target-derived neurotrophic factor for basal forebrain cholinergic neurons (Kosching, TINS, pp 570-573 (Nov/Dec [1986]).
While a number of animal homologues to NGF have become known, it was not until recently that an apparently distinct nerve growth factor was identified that nonetheless bears some homology to NGF (Leibrock et al., Nature 341:149 [1989]). This factor, called brain-derived neurotrophic factor (BDNF), was purified from pig brain, and a partial amino acid sequence determined both from the N-terminal end and from fragments purified after cleavages. The longest sequence, compiled from several overlapping fragments, was used to synthesize two sets of oligonucleotides that were used to prime the amplification of a pig genomic template using the polymerase chain reaction (PCR). The nucleotide sequence between the two primers was determined and used to synthesize specific primers for further PCRs on a complementary DNA template obtained by reverse transcription of total RNA isolated from the superior colliculus of the pig brain. The nucleotide sequence so obtained contained an open reading frame coding for a protein of 252 amino acids, starting with the first methionine codon found after four in-frame stop codons. Leibrock et al. speculate that there is no reason to think that BDNF and NGF should be the only members of a family of neurothrophic proteins having in common structural and functional characteristics, and the authors hope that these common structural features could be sued to aid the discovery of other members.
It is an object to identify other neurotrophic factors which bear homology to NGF and to obtain nucleic acid encoding such factors.
It is another object to synthesize such new factors in recombinant cell culture.
It is yet another object to provide derivatives and modified forms of such new factors.
It is an additional object to prepare immunogens for raising antibodies against such new factors, as well as to obtain antibodies capable of binding them.
Another object is to provide diagnostic and therapeutic compositions comprising such new factors or derivatives thereof and methods of therapeutic treatment.